In today's information age the glut of information available overwhelms many information systems. For instance, wideband electro-optic modulators have been demonstrated that are capable of over a 60 GHz instantaneous bandwidth. Such large quantities of information makes finding specific data difficult. Filtering of radio frequency information in the optical domain has been performed using: Fabry Perot filters, ring/spherical waveguide resonators, time delay filters, and radio frequency filters.
Fabry Perot Filters cannot produce a narrow transmission filter function, but instead filter in the 10's of GHz and therefore cannot notch filter around a narrow bandpass. Fabry Perot filters possess small free spectral ranges that may lead to multiple filter bandpass groups in a particular radio frequency channel. Ring/spherical resonators require extreme fabrication precision that has not been demonstrated to date. In addition, ring/spherical resonators are fragile and thus challenging to package. Current state of the art ring/spherical resonators can filter RF signals in the high MHz to GHz regime. Also, ring/spherical resonator structures are built in planar constructions that possess different mode fields than do optical fibers, creating excessive optical insertion loss. Time delay filters require a means to accurately tune/adjust time of arrival or path length along a number of paths to tune filters, thus requiring banks of control and switching functions to create/control/modify time delays. To date high bit time delays are not available and low bit time delays are not size, weight, and/or power compatible. Traditional radio frequency filters are bulky and heavy and cannot be adjusted quickly.